This section provides background information related to the present disclosure which is not necessarily prior art. Some modern navigation systems have an off-road mode that may display a route to a chosen destination; however, such navigation systems are not without their share of limitations.
As an example, FIG. 1 is a prior art plan view of an off-road navigation path 2 demarking a current vehicle position 4, path waypoints 6, 8, 10, 12 and recommended trajectories 14, 16, 18, 20, 22 or routes for vehicle travel. More specifically, trajectory 14 is a recommended path of travel from an original or current vehicle location 4 to the first waypoint 6, trajectory 16 is a recommended path of travel between first waypoint 6 and second waypoint 8, trajectory 18 is a recommended path of travel between second waypoint 8 and third waypoint 10, trajectory 20 is a recommended path of travel between third waypoint 10 and fourth waypoint 12, and trajectory 22 is a recommended path of travel between fourth waypoint 12 and destination 24. While such off-road navigation paths displayed by navigation systems in an off-road mode have been satisfactory, they are not without limitations.
One limitation of current off-road modes of navigation systems is that such waypoints 6, 8, 10, 12 and destination 24 become displayed set points only after a user selects such points from a navigation system screen that displays a map of a desired off-road area. Because roads are non-existent in an off-road area, a user must self-select waypoints. Straight line trajectories 14, 16, 18, 20, 22 are displayed on the display upon selecting waypoints as described above, but are merely reference trajectories because such trajectories, and intermediate waypoints and the destination, are along an off-road path whose actual terrain is unknown and potentially inappropriate or impossible for vehicle travel. For instance, any of the above noted trajectories may be through a river that is deeper than an off-road vehicle is capable of traveling, or the ground clearance of the terrain may be more than an off-road vehicle is capable of accommodating. While the waypoints and straight-line trajectories may be stored and re-used, such a route may be incorrect or wrong due to such inhospitable terrain noted above. If a vehicle driver desires to correct the positions of waypoints and the destination along an off-road path, he or she must manually set memory points as new waypoints and a new destination as he or she traverses the off-road terrain and then store such set points in navigation system memory as a new route. Thus, current system trajectory selection may not be accurate or appropriate for a vehicle.
Another limitation of current off-road navigation modes of vehicle navigation systems is that voice guidance may also be inaccurate and difficult to follow. As an example, when a vehicle approaches waypoint 6 on FIG. 1, the vehicle may be deemed to actually reach waypoint 6 when the vehicle travels within an area 26 around waypoint 6. When the vehicle enters area 26, a voice guidance system may then instruct the vehicle driver, for example, “to turn 45 degrees to the right” in order to proceed to the next waypoint, such as waypoint 8; however, depending upon where in area 26 the voice guidance instructs the driver to turn, the driver may begin along a path such as trajectory 30, which is not along originally prescribed path 16 and not in line to intersect with waypoint 8. If a vehicle driver were to follow such voice directions, arriving within area 28 around destination 24 may be difficult or impossible to achieve.
What is needed then is an off-road navigation system that does not suffer from the above limitations.